Beveling from tutorial not working for me, can't find a work around
There seem to be some vertices in the middle of the faces of the floor of the chest, inside and out, which are not there in the tutorial. There are edges extending to them from your new edge-loops, and the corners. The floor of the chest should be a plain Ngon. I would go back to before introducing the new edge loops, and check for them.

While you're back there check for other vertices that shouldn't be there.. both ones you can see, and ones you can't. (Right-click to select a vertex, G to move it, right-click again to drop it back where it came from if it hasn't revealed a duplicate, or otherwise acted strangely.)

In edit mode, CtrlV -> Edge Menu > 'Remove Doubles' to get rid of coincident extra vertices.

You may have to delete the floor faces altogether and replace them by Alt - selecting the edges on the perimeters of the new holes, and hitting F to fill.